Hitherto, an acetoxyethyl methacrylate has been well known as a (meth)acrylate having a terminal acetylacetonate group in the molecule.
The acetoxyethyl methacrylate is represented by the following formula (III): ##STR1##
U.S. Pat. No. 3,459,790 describes that the above-described compound (III) can be prepared by the reaction of 2-hydroxyethyl methacrylate with diketene, and the compound can be copolymerized with butyl acrylate, acrylic acid, etc., to obtain an acrylic copolymer having active protons.
U.S. Pat. No. 3,459,790 further describes that the acrylic copolymer can be used as a photosensitive material in the photographic field exhibiting a good dimensional stability and abrasion resistance.
On the other hand, U.S. Pat. No. 4,288,511 describes that the acrylic copolymer can be used in the photographic field as a hydrophilic vehicle for chelating acid dyes or dyeforming materials to provide a metallized dye image.
Still further, Japanese Unexamined Patent Publication (Kokai) 275356/1986 describes that the acrylic copolymer can be used as a photosensitive resin composition for resist by mixing with a polyacrylic acid, methyl methacrylate, trimethylolpropane triacrylate, and a photo-initiator, etc., Japanese Unexamined Patent Publication (Kokai) 156225/1993 also describes that the acrylic copolymer can be used as one liquid for a two-liquid adhesive by mixing with Epikote 828 which is a typical epi-bis epoxy resin.
Although the acetoxyethyl methacrylate represented by the formula (III) has the property of providing an excellent reactivity as a dispersant for pigments and inks, etc., it must be further improved in flexibility, anti-strippability from a substrate, compatibility with other polymers, and resistance to scratches.
On the other hand, requirements have recently begun to arise in the development of monomers and resins necessitating that they have more excellent characteristics and higher quality from the viewpoint of saving energy, preserving resources, and diversifying applications.
More specifically, there have been proposed monomers or polymers having a higher stability and higher sensitivity in the field of photosensitive materials, and water-based coatings, high-solid coatings, and UV-curable coatings in the field of coatings.
A (meth)acrylic copolymer obtained by the radical copolymerization of acetoxyethyl (meth)acrylate, acrylic acid, styrene, etc., is employed as adhesives or coatings for woodworking by being used together with a curing agent such as amines, for example.
Such adhesives or coatings are insufficient in stress relaxation during adhering and curing, resulting in considerably poor adhesion, however, and the resultant stripping of the coating layer from a substrate.
Furthermore, the copolymer is employed as coatings having weatherability, chemical resistance, water resistance, contamination resistance, and excellent curability by being used together with a curing agent such as isocyanates, melamines, etc.
It is difficult, however, for the copolymer to provide sufficiently flexible coating layers.
As described hereinabove, although the acetoxyethyl methacrylate monomer can be employed in various fields because of its unique reactivity, it has the disadvantages of insufficient flexibility, poor adhesion, abrasion resistance, compatibility with other resins, and stress relaxation, and these advantages must be improved.
In addition, in the case that it is employed as photosensitive material or dispersants for pigments in the form of emulsion, the acetoxyethyl methacrylate monomer is insufficient in its affinity to pigments and compatibility with other resins.
For the purpose of solving the above-mentioned disadvantages, as a result of an intensive investigation, the inventors of this invention have now found that it is possible to solve the problems by modifying a lactone-modified (meth)acrylate compound with diketene.